Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$95.29	7.645%	$102.5749	$102.57	$102.55	$102.60
Purchase #2	$54.29	4.626%	$56.8015	$56.80	$56.80	$56.80
Purchase #3	$232.61	10.316%	$256.606	$256.61	$256.60	$256.60
Purchase #4	$101.58	8.734%	$110.452	$110.45	$110.45	$110.50
Purchase #5	$127.56	7.522%	$137.1551	$137.16	$137.15	$137.20
Purchase #6	$233.83	7.129%	$250.4997	$250.50	$250.50	$250.50
Purchase #7	$125.98	12.194%	$141.342	$141.34	$141.35	$141.30
7 purchase totals =	$971.14		$1,055.4312	$1,055.43	$1,055.40	$1,055.50